Auto populate calendar from data lists with color coordination across all dates

We use a manually filled excel calendar to manage military leaves and activities. I need a 12 month calendar, that will populate events from a single data source.

If possible,we would need:
*A Formula showing the category/action spanning across all the calendar days, between the start and end date, displayed with a preset category color.
*Ability to add multiple lines of category/actions (atleast 5) to each day.
*Formula for 12 month calendar that stays current each year.

I have attached an example of my manually filled calendar with an example of a simple auto populating calendar. If you could help my manual calendar become, auto populated from the leave
Start/end dates with the specified category color and names spanning across all the calendar dates, it would be awesome! Thanks!